1. Field of the Invention
The present invention relates to a device and a method to detect an impact on a blade of a gas turbine engine, in particular a blower blade.
2. Description of the Related Art
A gas turbine engine when it is mounted on an aircraft can be damaged by objects being sucked by the engine upon its use. Such objects can have various shapes, for example, birds, stones or ice.
After the objects being sucked, the latter circulate from upstream to downstream in the engine, while striking different engine elements. Such phenomenon is known as “ingestion of foreign bodies.”
Depending on the nature, the density and the relative speed of the bodies ingested by the engine, some parts of the engine can be more or less damaged.
In order to keep a high degree of safety and reliability of the engine upon its use, it is necessary to detect the damages generated by such ingestions so as to repair or replace the engine elements being damaged.
For commercial flights having passengers, the gas turbine engines are visually inspected before each flight. This inspection presents several drawbacks. First of all, this visual inspection cannot allow a totally reliable detection, since the operators cannot see small damages, the latter being difficult to notice. Secondly, when damage is detected, it is necessary to make immediately maintenance operations, thereby needing to immobilize the aircraft and, consequently, delaying the departure thereof. This later detection of the effects of an ingestion of a foreign body thus leads to trouble for the passengers who have to embark on said aircraft.
It is known from the Patent Application FR2840358 A1 from SNECMA to provide a damage detection system for a rotor of an aircraft engine, comprising measurements means for the vibration and the speed of the rotor upon a determined flight. However, such a system does not have the required precision to detect the ingestion of a foreign body.
It is known from the Patent Application EP 1312766 A2 from ROLLS-ROYCE to provide an impact detection method on a rotor blade, wherein the rotor speed fall is measured to emit an alarm. Such detection presents this drawback to be a little discriminating. Indeed, in case of an engine pumping, the rotor speed decreases and an alarm is emitted whereas no body has been ingested. In order to eliminate such drawback, the Patent Application EP 1312766 A2 learns to add sensors to measure the torsion angle of the engine and to thus improve the precision of the method. Such method, with numerous sensors, is not satisfactory and does not allow an ingestion of a foreign body to be detected on a precise and reliable way.